Vent valve required?

[Schmill]

I'm installing a shower pump in the airing cupboard.
At the moment there is a 15mm hot feed that comes out of the top of the hotwater cylinder alongside the main 22mm feed. The 22mm then travels horizontally to the center of a T, where it travels vertically up as a vent, and vertically down to supply all the hot water outlets.

The 15mm pipe will travel horizontally, and then down to the shower pump on the floor of the airing cupboard.
My question is whether this 15mm pipe should have some kind of vent in it somewhere?

Obviously the pipe will be full of air when I first fit it, but when I then open the gate valve on the 15mm at the top of the hot water cylinder will this be sufficient to push the air out of the pipe?

[code:1]
VENT?
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|| Gate Valve
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| -------XX-| | ---- Some kind of flange....
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|| | T A N K |
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|------| | |
| PUMP | | |
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Only showing the HOT shower feed (to try and gain some clarity), also coming from the flange on the top of the tank is the 22mm pipework for other hot water outlets and that does have a pipe that vents over the cold water tank in the loft.

If it does need a vent in the place indicated, what sort of vent do I need to get?

Thanks

 

[echoes]

It shouldn't need a vent as you describe, since the design of the flange is precisely to prevent air entering the pump pipework.

Is it a Surrey flange?

P.S. Nice ASCII art!

 

[Schmill]

Thanks for your reply

I think it is a Surrey Flange, I couldn't remember the correct name for it.

I've now managed to take a photo of the current layout, which is hopefully an improvement on the ASCII art

Tank Top

• Schmill
• 12 Oct 2011
• 1

From this you can see the flange on the top of the tank, and from your picture I believe it is going to be a surrey flange. You can also see the 15mm shower feed going via the gate valve before crossing and rising up the wall were it used to enter the old power-shower directly.
It's now my intention to disconnect this at the Gate valve compression fitting and then run the new leg across to the wall, then DOWN to the pump.

I can see that the flange will (should!) stop air entering the pipework when it's all in operation, but how will the air that is in there after I fit it then get out? Can it go back through the flange, then up the 22mm and out through the vent that way, or will the water pressure in the 15mm pipe be sufficient (after I open the gate valve!) to 'push' all that air down the pipe, through the pump, and then back out via the shower?

Thanks

 

[echoes]

Assuming that it is a Surrey flange...

Once the pump is in, and before it is plugged in, you should prime it by directing the exit pipes from the pump into a bowl: this should remove any air and ensure the pump is full of water prior to use.

Also usual to have a 22mm feed to the pump rather than 15mm, but such a short feed would probably meet the pump manufacturer's requirements. If you keep the 15mm feed, I would change that gate valve for a full-bore lever isolating valve, just in case it doesn't completely open full-bore (and old gate valves sometimes refuse to close completely).

 

[Schmill]

I'm happy to presume it is a surrey flange, as it is that same feed that was previously feeding the powershower that was in the bathroom originally.
The cold feed from the loft is also only 15mm, but again that is fairly short as the cold water storage tank is in the loft directly above the airing cupboard, so it comes straight down the wall (previously to the power-shower), and will now continue to floor level where the pump is sited.

Thanks for the info regarding the gate valve, I didn't realise they were prone to such issues, the airing cupboard is full of them! However, I do know that this one completely shuts at the moment, as it is all that is stopping the hot water tank emptying into the aircupboard as the old shower feed is cut and has been for some time!
If I wanted to replace it, what is the recommended method for doing so? Is it just a case of switching off the cold feed to the hot water tank, then using hot water from a tap somewhere until the flow stops? I'm guessing I'll still get some water leakage from that point if I take the gate valve off, but will the above stop the tank spewing it contents into the cupboard?

Thanks!

 

[echoes]

Lucky man with reliable gate valves - I have 2 in my airing cupboard; they are 50 years old and each lets an annoying dribble through!

Turn off cold feed to tank, open hot tap and wait for flow to stop.

I would also run a bucket-full out of the bottom of the cylinder's drain cock (they sometimes stick) to be on the safe/dry/unscalded side, since the pipework at the immediate top of the cylinder will still contain some water.

Or cut that 15mm pipe after the closed gate valve, open gate valve slowly and catch contents in bucket and on wife's best clean towels.

 

[Schmill]

Sounds like a plan, especially as I know I've had gate valves get stuck before, (when I moved in they hadn't been moved in who-knows-how-long, some freed up, some didn't!).

Sooo.... taking a look at good ol' screwfix, any idea what the difference is between these 2 items, (except the price!)

http://www.screwfix.com/p/full-bore-lever-ball-valve-15mm/80413

http://www.screwfix.com/p/full-bore-lever-ball-valve-15mm/13103

 

[echoes]

Sounds like a plan, especially as I know I've had gate valves get stuck before, (when I moved in they hadn't been moved in who-knows-how-long, some freed up, some didn't!).

Sooo.... taking a look at good ol' screwfix, any idea what the difference is between these 2 items, (except the price!)

http://www.screwfix.com/p/full-bore-lever-ball-valve-15mm/80413

http://www.screwfix.com/p/full-bore-lever-ball-valve-15mm/13103

Not much! Slight quality differences maybe? The Pegler ones are very good, but pricey: http://www.screwfix.com/p/pegler-ball-valve-red-15mm/21289

 

[Schmill]

EDIT

Not much! Slight quality differences maybe? The Pegler ones are very good, but pricey: http://www.screwfix.com/p/pegler-ball-valve-red-15mm/21289

Seems availability is the difference too....
END EDIT

Cheers, might slap a couple of those on then.

Actually, that neatly leads me to another question

Is it 'standard' to put a set of valves on the supply side of the pump, AND on the feed-to-shower side? I'm thinking for servicing / changing the pump in the future. I don't imagine that a lot of water will be held in the outlet pipework to the shower, but also I think it might be more than I would want to have 'appearing' in the airing cupboard after undoing a joint, (might be more than a towel would cope with?)...

Thinking I may fit 4 of the lever valves, one on each of the inputs and outputs (hot and cold), least then if I have to remove / change the pump it is only the water held in the flexis that will come out...

 

[echoes]

It would certainly be standard to put a iso-valve on the supplies to the pump. The pump itself might come with valves on some or all of the flexi-connectors (of lesser quality).

Can't hurt to put them on the pump outputs though - you would never regret that move, but you might regret NOT having them at some point if you wanted to, for the reasons you mentioned.

 

[Agile]

I always like to see valves either side of a pump!

A few weeks ago I was called late to a leaking shower pump and the only way I could stop the leak was to borrow a working valve from the outlet in order to place it on the inlet where it was needed to stop the flow to the leaking end of the pump.

It was a nasty job in an inaccessible hole at end of bath.

I only went there because the owner who must have been about 80 said he had turned off the valve but it was still leaking.

On the phone I thought that at that age he had probably only turned it gently. In fact he had turned just a tight as I could!

Tony

 

[Schmill]

So a couple of these then?

http://www.screwfix.com/p/15mm-full-bore-isolating-valve/46860

Would they also be suitable for the input side, or should that be an 'easy to operate' one (with a lever or handle of some kind).

There are no isos on the pump flexis, I checked

 

[Schmill]

I actually did this a few weeks ago now, but I thought I would post a photo of the finished install in case anyone was interested

Shower Pump n Pipes

• Schmill
• 4 Nov 2011
• 1

Mira 3 ppt Shower pump, connecting pipes and full-bore iso valves.

Thanks again for all the advice!

The vented pipes are on the outlet side of the pump, and came with the pipework that was fitted to the pump when I got it second hand, (inlet side had nothing, and outlet side had the vertical vents, but had been chopped at the side exit of the reducing T's)